How a clever pump design saves 4 to 6hp

Tumultuous change? Maybe not but KRC has uncovered significant power losses with unique new test equipment

By Freddie Heaney, August 1, 2014, Photography Moore Good Ink

Kennesaw, GA: Recently, Chant, the engineering authority in electronic-hydraulic control systems, delivered new testing equipment to KRC, the engine pulley and power steering specialists. Strikingly, the tester, the first of its kind, has uncovered power steering system secrets reminiscent of aerodynamic revelations found in a wind tunnel.

A sophisticated one-off machine, it reveals that as engine speed increases in 1,000rpm increments one power steering pump can consume twice the power of another. [See Consumption tables at end of article.] The news, a defining moment for some, could contribute a decisive edge to not only NASCAR race teams who cherish every part of a horsepower gain but also to road race teams and short track oval racers.

Surprisingly, the tester further confirms that a small 5.9cc pump is capable of developing as much flow as a bigger pump while consuming half the horsepower. During recent tests with several GM-style power steering pumps modified for competition, the tester demonstrated they absorb around 3.6hp at 8,000rpm engine speed. By comparison KRC’s Pro Series 5.9cc pump used on Aston Martin’s victorious Le Mans sportscars absorbs 1.9hp. All pumps were tested with 125psi of load applied, which is the average pressure generated in a power steering system when operating in the straight ahead position.

Using data acquisition and a GoPro camera to identify power loses

Beyond this the tester not only measures pressure and flow and calculates power consumption but also duplicates the data acquired on a racing lap. By providing KRC with the relevant data acquisition—operating pressures and flow referenced to rpm—they can introduce the information to the tester and calculate horsepower consumption on each lap. Better still, if the data acquisition is synchronized with a GoPro video camera, pressures, flow, tire and steering loads, horsepower consumption etc., are all recorded and can be visually identified at any given position on the track.

Turn 4, for example, might portray the racecar at its most deficient with data showing, say, 500psi of pressure and 2.3 gallons per minute of flow, equating to consumption of 4hp. However, such deficiencies might easily be corrected by simply using a different pulley diameter. Moreover the tester will also check the data over endurance race distances, monitoring heat generated within the power steering system.

As most competent steering technicians might suspect, the test equipment demonstrates that the power steering system’s greatest efficiency is achieved when the pump is operating between 3,000 and 5,000rpm. It follows, if an engine operates mostly at 8,000rpm, the power steering pump would function more efficiently at around half engine speed.

Then…there’s the feel deal:

The most persistent complaint among magazine road-vehicle testers of fast sports cars with electric power steering is lack of feel: “…accurate steering but little feel…the electric steering robs the car of its feel…it’s compromised by its synthetic feel” and so forth.

Hydraulic power steering pumps on the other hand can exhibit a great deal of feel and are usually free of such criticism. Importantly, they also provide accurate feedback of forces acting upon the front wheels. Nonetheless, they must be designed to provide adequate flow when the engine is idling. As a result, the pump often moves much more fluid than necessary when the engine is operating at faster speeds.

Though it’s not clear how they achieved it, KRC somehow manage to retard flow rates with increasing engine revs. As a result “feel” qualities are preserved even as engine revs rise.

What is known is how they create race car feel for individual drivers. This is achieved by offering optional flow control valves. These flow valves, nine in number, work like jets in a carburetor. Different orifices regulate fluid transfer. Those marked B, C, D, or E, increase flow rate up to 12 liters per minute in one-liter increments. The higher letter indicates greater hydraulic assistance but less feel. On the other hand, flow valves marked with numbers 4, 5, 6, and 7 provide less assistance but greater feel. Simply select the flow valve that gives you the steering feel you like best.

No one who enjoys the thrill of driving, particularly race car driving, ever tires of the supreme and lasting pleasure of real steering feel.